ANATOMICAL, CHEMICAL, AND ECOLOGICAL FACTORS AFFECTING TREE SPECIES CHOICE IN DENDROCHEMISTRY STUDIES

Recently, element concentrations in tree rings have been used to monit or metal contamination, fertilization, and the effects of acid precipi tation on soils. This has stimulated interest in which tree species ma y be suitable for use in studies of long-term trends in environmental chemistry. Potential radial translocation of elements across ring boun daries can be a confounding factor in assessing environmental change. Thus, the selection of species which minimizes radial translocation of elements can be critical to the success of dendrochemical research. C riteria for the selection of species with characteristics favorable fo r dendrochemical analysis are categorized into (i) habitat-based facto rs, (ii) xylem-based factors, and (iii) element-based factors. Species with a wide geographic range and ecological amplitude provide an adva ntage in calibration and better controls on the effects of soil chemis try on element concentrations. The most important xylem-based criteria are heartwood moisture content, permeability, and the nature of the s apwood-heartwood transition. The element of experimental interest is i mportant in determining which tree species will be suitable because al l elements are not equally mobile or detectable in the xylem. Ideally, the tree species selected for dendrochemical study will be long-lived , grow on a wide range of sites over a large geographic distribution, have a distinct heartwood with a low number of rings in the sapwood, a low heartwood moisture content, and have low radial permeability. Rec ommended temperate zone North American species include white oak (Quer cus alba L.), post oak (Q. stellata Wangenh.), eastern redcedar (Junip erus virginiana L.), old-growth Douglas-fir [Pseudotsuga menziesii (Mi rb.) Franco] and big sagebrush (Artemisia tridentata Nutt.). In additi on, species such as bristlecone pine (Pinus aristata Engelm. syn. long aeva), old-growth redwood [Sequoia sempervirens (D. Don) Endl.], and g iant sequoia [S. gigantea (Lindl.) Deene] may be suitable for local pu rposes.